AC vs. DC Stick Part 3
So, why DC? What is it about welding with DC stick that is so special? That’s the question we often get. As we mentioned before, experience is the best way to answer this. It’s easier to “see” and believe.
When we break the welding down into what is actually going on, things are a little more tangible. The AC arc is actually cycling between + and negative polarity, 60 times a second. That means the arc is actually extinguishing itself and restarting 60 times a second. Now, of course, that would automatically make the arc sound different (louder). But it would also make the arc a lot more violent.
Another issue is that it also requires a lot more amperage to weld with an AC arc. The alternating current actually reduces the heat going into the puddle and cools the weld off as arc literally extinguishes several times a second. Another issue created by the use of the AC arc, is the problem of contamination. The AC arc due to its nature does not provide as pure or clean of a weld. It’s more likely to have inclusions and porosity. It’s more likely to be weak and not create a sound joint. That’s not to say an AC weld can’t be made strong, as it can, but it won’t be as strong as a DC weld where the current is constantly flowing in a single direction.
A less noticeable side effect of using AC is the flux can be a lot more difficult to remove. The great majority of welding rods either aren’t rated for AC only use or they don’t perform as well on DC. This is due to flux type and filler metal chemistry. Now, I could go on, because I don’t want to completely stack the deck in DC’s favor. But I struggle to find one nice thing to say about AC buzz boxes, other than they do make a nice boat anchor.